re
gas. The propellers became almost invisible blades of light and shadow,
and the aeroplane began moving over the grassy field. The mechanic had
sprung out of the way, pulling Mr. Damon with him.

"Come back! Come back! Wait a minute, Tom Swift! Bless my pansy
blossoms, I want to tell you something!" cried the little man.

But Tom Swift was away and out of hearing. He had started on his sky
ride with Mary Nestor.

CHAPTER II

A NEW IDEA

Any one who has taken a flight in an aeroplane or gone up in a balloon,
will know exactly how Mary Nestor felt on this, her first sky ride of
any distance. For a moment, as she looked over the side of the machine,
she had a distinct impression, not that she was going up, but that some
one had pulled the earth down from beneath her and, at the same time,
given her a shove off into space. Such is the first sensation of going
aloft. Then the rush of air all about her, the slightly swaying motion
of the craft, and the vibration caused by the motor took her attention.
But the sensation of the earth dropping away from beneath her remained
with Mary for some time.

This sensation is much greater in a balloon than in an aeroplane, for a
balloon, unless there is a strong wind blowing, goes straight up, while
an aeroplane ascends on a long slant, and always into the teeth of the
wind, to take advantage of its lifting power on the underside of the
planes. The reason for this sensation--that of the earth's dropping
down, instead of one's feeling, what really happens, that one is
ascending--is because there are no objects by which comparison can be
made. If one starts off on the earth's surface at slow, or at great
speed, one passes stationary objects--houses, posts, trees, and the
like--and judges the speed by the rapidity with which these are left
behind.

Going up is unlike this. There is nothing to pass. One simply cleaves
the air, and only as it rushes past can one be sure of movement. And as
the air is void of color and form, there is no sensation of passing
anything.

So Mary Nestor, as she shot into the air with Tom Swift, had a
sensation as though the earth were dropping from beneath her. For a
moment she felt as though she were in some vast void--floating in
space--and she had a great fear. Then she calmed herself. She looked at
Tom sitting in front of her. Of course, all she could see was his back,
but it looked to be a very sturdy back, indeed, and he sat there in the